Tom, Dick and Harry, for one (4)
I believe the answer is:
trio
'tom dick and harry for one' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for trio that I've seen before include "Piece for three players" , "Three together" , "Small group playing" , "Three of a kind" , "Group of Magi?" .)